Benzidine positive multicentric eosinophilic colonies in human blood mimicking erythroid bursts.

When normal human mononuclear blood cells are cultured in plasma clot or methylcellulose in the presence of erythropoietin, two types of benzidine positive multicentric colonies can be recognized in the light microscope at high magnification: one containing diffusely stained cells with the morphology of erythroblasts (erythroid bursts), and another containing diffusely and/or granular stained benzidine positive cells with a morphology of neutrophils/macrophages. Based on their cytochemical properties, lack of inhibition of the benzidine reaction by potassium cyanide, and strong granular staining with luxol fast blue and alkaline eosin, the cells from the latter are identified as eosinophils.